A Newark man was arrested yesterday afternoon after he threatened to kill his ex-girlfriend and then tried to evade police by hiding in a City Hall stairwell, authorities said.

Roger Miller, 21, was in the Municipal Court Building on Green Street with his ex-girlfriend, Malakia Woods, 25, of Newark, and her 3-year-old son, when he became upset that Woods' current boyfriend was also in court, city Det. Hubert Henderson said.

Woods asked her boyfriend and child to leave, but Miller followed them and hit the child on the back of his head, Henderson said. He then went back into the courtroom, where he threatened to kill Woods and also spat on her.

Woods alerted a nearby off-duty detective, who followed Miller as he left the court building and went into City Hall, Henderson said. Miller was eventually found and arrested in a stairwell.

Miller has been charged with simple assault under the state's domestic violence laws, terroristic threats, and endangering the welfare of a child and harassment, Henderson said.